OverlayCommand Class

[SerializableAttribute]
public class OverlayCommand : ImageCommand, 
	ISerializable

<SerializableAttribute>
Public Class OverlayCommand
	Inherits ImageCommand
	Implements ISerializable

private AtalaImage OverlayImage(string bottomFile, string topFile, Point position)
{
    // Make sure the files exist.
    if (!File.Exists(bottomFile))
        throw new FileNotFoundException("The bottom image file could not be found.", bottomFile);

    if (!File.Exists(topFile))
        throw new FileNotFoundException("The file to overlay could not be found.", topFile);

    // Load the bottom image.
    AtalaImage tmpImage = new AtalaImage(bottomFile);

    // Overlay does not support 4-bit bottom images.
    AtalaImage bottomImage = null;
    if (tmpImage.PixelFormat == PixelFormat.Pixel4bppIndexed)
    {
        bottomImage = tmpImage.GetChangedPixelFormat(PixelFormat.Pixel8bppIndexed);
        tmpImage.Dispose();
    }
    else
        bottomImage = tmpImage;

    // Load the top image.
    tmpImage = new AtalaImage(topFile);

    // If the bottom image is 16-bit per component, the top image must be the same.
    AtalaImage topImage = null;
    if (AtalaImage.PixelFormatIsTwoBytePerComponent(bottomImage.PixelFormat) && topImage.PixelFormat != bottomImage.PixelFormat)
    {
        topImage = tmpImage.GetChangedPixelFormat(bottomImage.PixelFormat);
        tmpImage.Dispose();
    }
    else
        topImage = tmpImage;

    OverlayCommand cmd = new OverlayCommand(topImage, position);
    cmd.ApplyToImage(bottomImage);

    // We are done with the top image.
    topImage.Dispose();

    return bottomImage;
}

Private Function OverlayImage(ByVal bottomFile As String, ByVal topFile As String, ByVal position As Point) As AtalaImage
    ' Make sure the files exist.
    If Not File.Exists(bottomFile) Then
        Throw New FileNotFoundException("The bottom image file could not be found.", bottomFile)
    End If

    If Not File.Exists(topFile) Then
        Throw New FileNotFoundException("The file to overlay could not be found.", topFile)
    End If

    ' Load the bottom image.
    Dim tmpImage As AtalaImage =  New AtalaImage(bottomFile) 

    ' Overlay does not support 4-bit bottom images.
    Dim bottomImage As AtalaImage =  Nothing 
    If tmpImage.PixelFormat = PixelFormat.Pixel4bppIndexed Then
        bottomImage = tmpImage.GetChangedPixelFormat(PixelFormat.Pixel8bppIndexed)
        tmpImage.Dispose()
    Else 
        bottomImage = tmpImage
    End If

    ' Load the top image.
    tmpImage = New AtalaImage(topFile)

    ' If the bottom image is 16-bit per component, the top image must be the same.
    Dim topImage As AtalaImage =  Nothing 
    If AtalaImage.PixelFormatIsTwoBytePerComponent(bottomImage.PixelFormat) And topImage.PixelFormat <> bottomImage.PixelFormat Then
        topImage = tmpImage.GetChangedPixelFormat(bottomImage.PixelFormat)
        tmpImage.Dispose()
    Else 
        topImage = tmpImage
    End If

    Dim cmd As OverlayCommand =  New OverlayCommand(topImage,position) 
    cmd.ApplyToImage(bottomImage)

    ' We are done with the top image.
    topImage.Dispose()

    Return bottomImage
End Function